1. Field of the Invention
This invention relates to a process for producing a plasminogen activator having a molecular weight of 45,000 to 68,000 in a high yield by utilizing cells derived from animals.
2. Description of the Prior Art
Plasminogen activators having a molecular weight of 45,000 to 68,000 are known as useful substances, and isolation of these activators in pure form from human urine has previously been known as a commercial process as described in Japanese Patent Publication No. 10232/1973 and U.S. Pat. No. 4,028,187.
However, the conventional process starting from human urine has several defects; (1) the quality of the raw material is variable, (2) it poses severe hygienic problems, and (3) large quantities of urine of healthy humans are difficult to obtain. In the course of finding a way to overcome such defects, it was noted that cells derived from human beings form plasminogen activators, as reported by E. Barnett and S. Baron Proc. Soc. Exper. Biol. & Med., 102 308 (1959). This method makes it possible to supply raw materials of constant quality in large amounts without a risk of pollution, and a technique of commercializing this method has been desired to be established. However, plasminogen activators formed by cells derived from human beings have a molecular weight of about 30,000, and activators having a molecular weight of about 50,000 can be produced only within a very short initial period after contacting the cells with a plasminogen activator-forming solution, as is reported, for example, in G. H. Barlow, Thrombosis Research, Vol. 1, page 201 (1972) and Vol. 11, page 149 (1977).
No method has yet been reported for producing plasminogen activators having a molecular weight of 45,000 to 68,000 in large quantities with good efficiency over a long period of time by utilizing cells derived from human beings.